Pilot injection for diesel engines



April 15, 1969 F. THOMA PILOT nwmcwzouroa DIESEL Enemss Filed Sept. 6; 1967 FIG. 7

INVENT OR FRANK THOMA ATTORNEYS Patented Apr. 15, 1969 3,438,359 PILOT INJECTION FOR DIESEL ENGINES Frank Thoma, Stuttgart-Fasanenhof, Germany, asslgnor to Daimler-Benz Aktiengesellschaft, Stuttgart-Unterturkheim, Germany Filed Sept. 6, 1967, Ser. No. 665,887 Claims priority, application Germany, Sept. 8, 1966, D 51,053 Int. Cl. F02b 3/00; F04b 13/02; F02m 39/00 US. Cl. 123-32 21 Claims ABSTRACT OF THE DISCLOSURE An installation for the control of the pre-injection by the use of an intermediate relief which is connected between an injection pump and an injection nozzle and which includes a control piston displaceable within a control cylinder in a first direction by the supply impulse of the injection pump and returned to its rest position by means of a spring force and/or the fuel supply pressure, whereby the control cylinder is provided with a first control port nearer its inlet which is in communication with the outlet leading to the nozzle and a second control port disposed axially behind the first port and further removed from the inlet which is in operative connection with an intermediate relief aperture; the control piston itself forms within the end area adjacent the inlet a closure piston portion, adjoined by a control cross section through which extends a cross bore terminating inwardly with an axial bore providing a communication with the spring space of the cylinder, disposed opposite the inlet; the mutually facing control edges of the two ports are spaced from one another a distance which is only slightly smaller than the axial dimension of the control cross section adjoining the closure piston while the over-all length of the control piston is such that the control edge formed by the inlet end thereof opens up a communication between the inlet and the first port shortly prior to abutment of the opposite end against an abutment in the spring space. The intermediate relief aperture may be connected either with a fuel storage space or with a fuel supply line or with a fuel return line.

Background of the invention The present invention relates to an installation for the control of the pre-injection by an intermediate relief, especially for motor vehicle internal combustion engines of the injection type, which is alternately connected between an injection pump and an injection nozzle of the injection system.

The German application D46,8 l2 Ia/46c2, filed in the name of the assignee of the present application relates to an installation for the control of the pre-injection by intermediate relief, especially for motor vehicle internal combustion engines, which is connected between an injection pump and an injection nozzle and includes a control piston displaced in one direction by a supply impulse of the injection pump and moved back by a spring 'force and/or fuel supply pressure, which control piston effects the intermediate release and whose one end is constructed as closure piston closing off a control cross section of a control cylinder connected with a lateral outlet to the nozzle during the intermediate relief. This type of installation which is described in the aforementioned German application as its second embodiment has the advantage with respect to the installation described therein as the first embodiment that the outlet to the injection nozzle is closed off during the intermediate relief so that with an excessive resistance that might eventually occur in the intermediate relief line, the injection nozzle cannot open. However, an installation according to the second embodiment of the aforementioned application requires a large number of control cross sections and cross bores.

Summary of the invention The present invention aims at reducing the expenditures for such a type of control installation by a reduction of the number of control cross sections at the control cylinder and at the control piston as well as the number of cross bores. The present invention achieves this purpose in that the closure piston is constituted by an inlet end region of the control piston which is adjoined by a control cross section of the control piston which, in turn, is operatively connected with a spring space of the control cylinder, disposed opposite the inlet side and containing a return-spring, by way of an axial control piston bore which terminates in a cross bore extending through the control cross section, in that the control cylinder is provided with two control cross sections disposed axially one behind the other, of which the control cross section closer to the inlet is operatively connected with the outlet to the injection nozzle and of which the control cross section opposite the inlet is operatively connected with an intermediate relief aperture, and in that mutually facing internal control edges of the two control cross sections have a spacing from one another which is only slightly smaller than the length of the control cross section adjoining the closure piston, while the over-all length of the control piston is so dimensioned that an inlet end of the control piston valves as control edge to open up a cylinder space on the inlet side with respect to the inlet control cross section shortly prior to the abutment of an end of the control piston opposite to the inlet against an abutment arranged in the spring space. It is thereby recommended according to the present invention that the intermediate relief aperture leads to a closed fuel storage space which temporarily receives the intermediate relief volume under pressure and releases the same after the injection, as described in the aforementioned German application.

Accordingly, it is an object of the present invention to provide a control installation for the control of the preinjection, especially for motor vehicle internal combustion engines, which effectively eliminates the shortcomings and drawbacks encountered in the prior art constructions.

Another object of the present invention resides in the control installation for controlling the pre-injection in a fuel injection system for motor vehicle internal combustion engines of the type described above which considerably reduces the necessary expenditures for such installation by reducing the number of parts and control cross sections as well as control bores necessary therefor.

A further object of the present invention resides in a control installation for the control of the pre-injection by intermediate relief action which is both simple and compact in construction and utilizes a minimum of parts, yet assures completely reliable operation of the installation.

These and further objects, features, and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein:

FIGURE 1 is a partial axial cross-sectional view through a first embodiment of a control installation for the control of the pre-injection according to the present invention provided with intermediate relief into a fuel storage space and with throttle bores as throttle devices, with the parts thereof shown in a rest position during the beginning of the main injection;

FIGURE 2 is a partial axial cross-sectional view of the 3 installation illustrated in FIGURE 1 with the parts thereof in the position during intermediate relief;

FIGURE 3 is a partial axial cross-sectional view, similar to FIGURE 1, and illustrating the parts thereof in the position during the main injection;

FIGURE 4 is a partial axial cross-sectional view, similar to FIGURE 1, illustrating the parts thereof in the position during the emptying or discharge of the fuel storage space;

FIGURE 5 is a partial axial cross-sectional view, simi lar to FIGURE *1, showing the parts thereof during the re-filling of the spring space from the cylinder space on the inlet side;

FIGURE 6 is a partial axial cross-sectional view through a modified embodiment of a control installation for the pre-injection in accordance with the present invention provided with intermediate relief into a fuel storage space and with ground sections as throttling devices, with the parts thereof illustrated in a position correspondingto the position in FIGURE 1;

FIGURE 7 is a partial axial cross-sectional view, similar to FIGURE 6, and illustrating the parts thereof in the position during the main injection;

FIGURE 8 is a partial axial cross-sectional view through a third embodiment of a control installation for the control of the pre-injection in accordance with the present invention provided with intermediate relief into a fuel supply line, with the parts thereof corresponding to the rest position in FIGURE 1; and

FIGURE 9 is a partial axial cross-sectional view through a fourth embodiment of an installation for the control of the pre-injection in accordance with the present invention with intermediate relief into a return line and having a fuel supply line terminating in the spring space, with the parts thereof shown in the position corresponding to the rest position of FIGURE 1.

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate like parts, the control cylinder of the first embodiment (FIGS. l5) is provided with an inlet 1 at the end face thereof, to which an injection line (not shown) coming from an injection pump is adapted to be connected; the control cylinder contains a control piston 2 whose end area on the inlet side forms a closure piston 3 which is adjoined by a control cross section 4 of the control piston 2. The control cross section 4 is operatively connected by way of a radially extending cross bore 5 with a lower portion 6 of an axial control piston bore 6, 7 which terminates in a spring space 9 of the control cylinder, disposed opposite the inlet 1 and containing a return spring 8. The upper portion 7 of the control piston bore 6, 7, terminates in an inlet cylinder space 10 located on the inlet side and is separated from the lower portion 6 by a wall through which extends a first throttle bore 11.

The control cylinder has two control cross sections or ports 12 and 13 disposed axially one behind the other, of which the control cross section or port 12, disposed closer to the inlet 1, is connected with an outlet 14 leading to an injection nozzle (not shown) and the control section or port 13, more remote from the inlet 1, is connected with an intermediate relief aperture 15. Mutually facing inner control edges 16 and 17 of the control cross sections or ports 12 and 13 are at a distance 18 from one another which is only slightly smaller than a length 19 of the control cross section or port 4 of the control piston 2 which adjoins the closure piston 3. An over-all length 20 of the control piston 2 is so dimensioned that an inlet end 21 of the closure piston 3 valves as control edge the inlet cylinder space 10 in the opening sense with respect to the control cross section 12 of the control cylinder dis' posed closer to the inlet 1 shortly before an end 22 of the control piston 2, opposite the inlet 1, abuts against an abutment 23 arranged in the spring space 9. The intermediate relief aperture contains a second throttling bore 24 which connects the control cross section or port 13 opposite the inlet 1 with a fuel storage space 25 arranged adjacent the control cylinder and whose throttling corresponds approximately to the throttling of an injection nozzle. A third throttling bore 26 which extends radially through the closure piston 3, is disposed directly above and parallel to the wall accommodating the first throttling bore 11 and which connects the upper portion 7 of the control piston bore 6, 7 and therewith the inlet cylinder space 10 in a rest position of the control piston 2 with the control cross section or port 12 closer to the inlet 1. A fourth throttle bore 27 extends radially through the control piston 2 and connects, in a rest position of the control piston, the lower portion 6 of the axial bore 6, 7 thereof with the control cross section or port 13 of the control cylinder opposite the inlet 1.

Operation The operation of the installation described hereinabove is as follows:

The control piston 2 at first assumes the rest position illustrated in FIGURE 1 into which it is brought by the return spring 8, and the inlet cylinder space 10, the spring space 9 and the fuel storage space 25 are filled with fuel under static pressure. If a fuel injection impulse now arrives from the injection pump by way of the inlet 1, then the control piston 2 moves rapidly downwardly and displaces fuel out of the spring space 9 which flows off into the outlet 14 to the injection nozzle by way of the lower portion 6 of the axial control piston bore 6, 7, the cross bore 5, the control cross section 4 of the control piston 2 and the control cross section 12 of the control cylinder and thereby effects the pre-injection. The pre-injection lasts for such length of time until a position between the positions illustrated in FIGURES 1 and 2, a control edge 28 of the control cross section 4 which is disposed opposite the closure piston 3, passes over the inner control edge 17 of the control cross section 13 and thus opens the intermediate relief aperture 15 whereupon shortly there after a control edge of the control cross section 4 formed by the closure piston 3 passes over the inner control edge 16 of the control cross section 12 and thus closes off the outlet 14 to the injection nozzle. During the intermediate relief the fuel displaced out of the spring space 9 by the downwardly moving control piston 2 flows, as illustrated in dash line in FIGURE 2, along its path by way of the lower portion 6 of the axial control piston bore, the cross bore 5, the control cross section 4 of the control piston 2, and the control cross section 13 of the control cylinder through the throttling bore 26 of the intermediate relief aperture 15 into the fuel storage space 25 until an inlet end 21 of the closure piston 3 passes over an outer con trol edge 29 of the control cross section 12 in the lower end position of the control piston 2 as shown in FIGURE 3, and thus opens for the main injection a direct connection between the inlet cylinder space 10 and the outlet 14 to the injection nozzle. After the end of the injection impulse supplied from the injection pump, the fuel compressed in the fuel storage space 25 and in the spring space 9 as well as the return spring 8 drive the control piston 2 by way of the intermediate position illustrated in FIGURE 4, in which the fuel flows back from the storage space 25 into the spring space 9, and by way of the intermediate position illustrated in FIGURE 5, in which the control cross section 13 opposite the inlet 1 is again closed off while the control cross section 12 closer to the inlet 1 again comes into communication with the spring space 9, back into the rest position illustrated in FIGURE 1, whereby fuel continues to flow by way of the throttle bore 26 from the inlet cylinder space 10 into the spring space 9. In this rest position, the throttle bore 27 is opened up by passing over an outer control edge 30 of the control cross section 13 so that any pressure differences which may be present possibly between the fuel in the fuel storage space 25 and the fuel in the spring space 9 are equalized.

In the second embodiment which corresponds essentially to the first embodiment and whose parts corresponding to the parts of the first embodiment are designated by the printed reference numerals, a number of throttling devices is constructed as ground surfaces or sections in seating surfaces of the control piston. A ground section 31 extending in an outer surface of the closure piston 3' replaces the throttle bore 26 in the closure piston 3 of the first embodiment. The ground section 31 extends with its lower end into the control cross section or port 12 of the control cylinder connected with the outlet 14' in the rest position of the control piston 2' illustrated in FIGURE 6 and with its upper end into an additional control cross section 32 provided in the inlet cylinder space 10'. A second ground section 33 terminating in the control cross section 4 of the control piston 2 connects, in the lower end position of the control piston illustrated in FIGURE 7, the control cross section 13' in communication with the fuel storage space 25', with the spring space 9' and thus replaces the throttle bore 27 of the first embodiment. As to the rest, the embodiment of FIG URES 6 and 7 is similar to the embodiment of FIG- URES 1 through 5 and operates in an analogous manner.

In the third embodiment of FIGURE 8, an intermediate relief aperture 34 is connected with a fuel supply line 35 of the injection pump. Also, the spring space 36 is again re-filled by way of the fuel supply line 35. As to the rest, the third embodiment illustrated in FIGURE 8 is similar to the two previously described embodiments.

In the fourth embodiment illustrated in FIGURE 9, the intermediate relief aperture 37 is connected by way of a first check valve 38 with a fuel return line 39, and the refilling of the spring space 40 takes place by way of a second check valve 41 from a fuel supply line 42. Again, as to the rest of the embodiment of FIGURE 9, what has been said hereinabove with respect to the other embodiments also applies to this embodiment.

While I have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art, and I therefore do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. An installation for the control of the pre-injection by intermediate relief, especially for motor vehicle internal combustion engines, which is operatively connected between an injection pump and an injection nozzle, comprising control cylinder means, control piston means within said control cylinder means which is displaced in one direction by the supply impulse of the injection pump and is returned to its rest position after completion of the main injection, said control piston effecting the intermediate relief, said cylinder means being provided with inlet means and with a first and a second control cross section means disposed axially one behind the other, the first cross section means which is disposed closer to the inlet means being operatively connected with a lateral outlet means leading to the nozzle, closure piston means constituted by an inlet end area of the control piston means and operable to close said first control cross section means during intermediate relief, said closure piston means being adjoined by a control cross section of the control piston means, said cylinder means being provided with a spring space at the end opposite the inlet means and containing a return spring, the control cross sec-tion of the control piston means being operatively connected with said spring space by way of axial control piston bore means and cross bore means extending through the control cross section of the control piston means and terminating in said axial control piston bore means, the second control cross section means of the control cylinder means which is disposed opposite the inlet means being operatively connected with intermediate relief aperture means, the first and second control cross section means of the control cylinder means having mutually facing inner control edges spaced from one another by a distance which is only slightly smaller than the length of the control cross section of the piston means adjoining the closure piston means, and the over-all length of the control piston means being so dimensioned that an inlet end of the closure piston means, which is operable as control edge, opens shortly prior to the abutment of the opposite end of the control piston means against an abutment in the spring space, a cylinder space formed on the inlet side with respect to the first control cross section means.

2. An installation according to claim 1, wherein said intermediate relief aperture means leads to a closed fuel storage space.

'3. An installation according to claim 1, wherein the intermediate relief aperture means is opera-tively connected with a fuel supply line.

4. An installation according to claim '1, wherein the intermediate relief aperture means is operatively connected by way of a check valve with a return fuel line, and wherein the spring space is operatively connected "by way of a further check valve with a fuel supply line.

5. An installation according to claim 1, further comprising first throttling means at the closure piston means which operatively connects with relatively high throttling the inlet cylinder space with the spring space.

6. An installation according to claim 1, wherein the intermediate relief aperture means is provided in effect with a second throttling means corresponding approximately to the throttling of the injection nozzle.

7. An installation according to claim 1, wherein said closure piston means is provided with throttling means which in the rest position of the control piston means operatively connects the inlet cylinder space with the first-control cross section means of the control cylinder means.

8. An installation according to claim 7, wherein said intermediate relief aperture means leads to a closed fuel storage space.

9. An installation according to claim 7, wherein the intermediate relief aperture means is operatively connected with a fuel supply line.

10. An installation according to claim 1, wherein said control piston means is provided with a further equalization throttling means for the fuel storage space which extends through the control piston. means within the area of its axial control piston bore means and which operatively connects the same in the rest position of the control piston means with the second control cross section means of the control cylinder means.

11. An installation according to claim 10', wherein said intermediate relief aperture means leads to a closed fuel storage space.

12. An installation according to claim 5, wherein the intermediate relief aperture means is provided in effect with a second throttling means corresponding approximately to the throttling of the injection nozzle.

13. An installation according to claim 12, wherein said closure piston means is provided with throttling means which in the rest position of the control piston means operatively connects the inlet cylinder space with the first-control cross section means of the control cylinder means.

14. An installation according to claim 10, wherein the throttling means are constituted by throttling bores.

15. An installation according to claim 13, wherein the throttling means are constituted by cut sections in the seating surfaces of the control piston means.

16. An installation according to claim 13, wherein the throttling means are cut sections in the seating surfaces of the control cylinder means.

17. An installation according to claim 13, wherein said control piston means is provided with a further equalization throttling means for the fuel storage space which extends through the control piston means within the area of its axial control piston bore means and which operatively connects the same in the rest position of the control piston means with the second control cross section means of the control cylinder means.

18. An installation according to claim 17, wherein the throttling means are constituted by throttling bores.

19. An installation according to claim 17, wherein the 10 throttling means are constituted by cut sections in the seating surfaces of the control piston means.

20. An installation according to claim 17, wherein the throttling means are cut sections in the seating surfaces of the control cylinder means.

21. An installation according to claim 17, wherein said intermediate relief aperture means leads to a closed fuel storage space.

References Cited UNITED STATES PATENTS 2,173,813 9/1939 Bischof. 3,387,597 6/1968 Wirsching a- 123-32 3,392,715 7/ 1968 Thoma 123-139 LAURENCE M. GOODRIDGE, Primary Examiner.

US. Cl. X.R. 

